Abstract
The synthesis of electrocatalysts for the chemical reactions of hydrogen systems (e.g. fuel cells and electrolyzer systems) continues to be a significant area of research in the renewable energy community. The kinetics of hydrogen reactions decrease by two orders of magnitude in alkaline environments compared to acidic, which has rendered significant challenges in the development as catalysts of alkaline fuel cell systems[1,2]. Chemical vapor deposition (CVD) is a conventional synthesis process applied to manufacture electrocatalysts[3,4]. In this study, a modified form known as "Poor Man's" CVD (PMCVD) is utilized, to further its impact in electrochemical catalyst development. This work assesses the deposition mechanism as well as its ability to develop tuneable catalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) for alkaline media.
In our last efforts, we showed Pt based catalysts synthesized using the PMCVD method exhibited higher activities for the HOR/HER in alkaline media than commercially available catalysts[5]. The performance was attributed to the tunability of crystallite size by varying the temperature and pressure of the PMCVD process. In an effort to further understand the deposition mechanism of this processes, we investigated Pt catalysts on various carbon supports. In doing so, Pt was deposited on three supports: XC-72, Acetylene Black, and Graphitized Nanoplatelets with 30% Pt by weight. The carbons varied in both surface areas and degree of graphitization. This work will summarize the HOR/HER activities of these three Pt/C catalysts in alkaline media. It will also help elucidate the impact of the deposition mechanism as a function of each support based on their material properties.
[1] Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energ. Environ. Sci. 7, 2255–2260 (2014).
[2] Sheng, W. et al. Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes." Electrochem. Soc. 2010 volume 157, issue 11, B1529-B1536
[3] Garcia, Vargas, et al., "Chemical Vapor Deposition of Iridium, platinum, Rhodium, and Palladium." Materials Transactions, Vol. 44, No. 9 (2003) pp. 1717 to 1728
[4] Serp, Philppe, et. al., "Chemical Vapor Deposition Methods for the Controlled Preparation of Supported Catalytic Materials." Chem. Rev. 2002, 102, 3085−3128
[5] Williams, S. et. al. "Synthesis and Characterization of Electrocatalysts for the Hydrogen Evolution Reaction in Alkaline Environment." ECS Abstract Fall 2019.
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